(append_to_g_password_keyfilehash())): warning: strcat() is almost always misused, please use strlcat()

[dertuxmalwieder]

Trying to build zpaqfranz 63.5 on OpenBSD:

ld.lld: warning: zpaqfranz.cpp(/tmp/zpaqfranz-4279cf.o:(append_to_g_password_keyfilehash())): warning: strcpy() is almost always misused, please use strlcpy()
ld.lld: warning: zpaqfranz.cpp(/tmp/zpaqfranz-4279cf.o:(append_to_g_password_keyfilehash())): warning: strcat() is almost always misused, please use strlcat()

Related: #54

[fcorbelli]

I'm fighting with VHD-NTFS structures, I'll fix later